The present invention relates generally to fillets used with a turbine rotor blade, and more specifically, to a fillet used between an airfoil and tip shroud of a turbine rotor blade.
At least some known turbine rotor blades include an airfoil, a platform, a shank, a dovetail extending along a radial inner end portion of the shank, and a tip shroud formed at a tip of the airfoil. On at least some known airfoils, integral tip shrouds are included on a radially outer end of the airfoil to define a portion of a passage through which hot combustion gasses must flow. Known tip shrouds and airfoils typically include a fillet having a predetermined size and shape at the intersection of the tip shroud and airfoil.
During operation, the connection formed between such a tip shroud and airfoil of a rotor blade become highly stressed due to rotationally induced centrifugal and mechanical forces. The fillets formed between the tip shroud and the airfoil are shaped to reduce the stress concentrations that occur in this region. However, known fillet shapes still allow the buildup of stress concentrations that reduce the effective life of the component. Further, known fillets may reduce engine efficiency due to drag forces and obstruction produced by the fillets. Consequently, there is a need for improved fillet shapes that further reduce stress concentrations, while also aerodynamically performing so to promote engine efficiency.